Displays such as CRT (cathode ray tube) displays, LCDs (liquid crystal displays), PDPs (plasma display panels), EL (electroluminescent) displays are each required to have a display surface provided with various functions of anti-scratch, anti-reflection for ambient light, anti-soil, and the like. To the display surface of these displays, protective members such as a protective film are attached in some cases. As this protective film, one showing anti-reflection for ambient light is used, thereby giving the needed functions to the display surface at one time.
TAC (triacetyl cellulose), which scarcely has birefringence and is excellent in moisture permeability and high adhesion, is often used as a material for the protective film. It is known that for anti-reflection of ambient light, for example, this TAC film is provided with AG (anti-glare) treatment or LR (low reflection) treatment. According to the AG treatment, fine grooves are formed on the TAC film surface, and by utilizing light scattering effects, the anti-reflection is achieved. According to the LR treatment, a material with a refractive index different from that of the TAC film is applied on the TAC film, and by utilizing the effect of interference of light reflected by the TAC film surface and light reflected on the applied material surface, the anti-reflection is achieved.
Typically, LCDs include a polarizing plate on the outermost surface facing a user, and the polarizing plate is required to show the above-mentioned functions. Such a polarizing plate is produced by the following method, for example, as disclosed in Patent Document 1. First, a TAC film, which is a base, is fed from a roll and stretched in the longitudinal and/or transverse directions. A PVA (polyvinyl alcohol) film containing iodine molecules adsorbed thereto and oriented in the stretching direction(s) is fed from a roll. The TAC film is attached to one surface of the PVA film. Then another TAC film is attached to the other surface thereof. Thus the PVA film is sandwiched from the both sides by the respective TAC films. Finally, the obtained laminated sheet is subjected to embossing of microstructures.
The stretched PVA film functions as a polarizing film.
As a way of achieving low reflection on the display surface of a display device, a technology of, for example, as disclosed in Patent Document 2, providing the display surface with moth-eye structures composed of finely and closely formed undulated patterns is drawing attention. More specifically, the moth-eye structures include protrusions and recesses, a pitch of which is controlled to a visible light wavelength or smaller, i.e., a nanometer size (several tens to several hundreds nanometers). This allows a refractive index of light incident on the display surface to be continuously changed along the depth of the protrusion and recess. As a result, light reflectance on the display surface can be decreased.
As a method of forming the protrusions and recesses, a technology of transferring nanosized protrusions and recesses of a mold onto a resin material coated on a substrate by pressing the mold to the material surface, so-called nanoimprint technology, is drawing attention now. Thermal nanoimprint and UV (ultraviolet) nanoimprint are known as the nanoimprint technology. According to the UV nanoimprint, for example, a mold with nanosized protrusions and recesses is pressed to a UV-curable resin thin film formed on a transparent substrate to emboss the film with the mold surface pattern, and then the film is cured by UV radiation, thereby producing a nanoimprint film with nanostructures in the inverse shape of the mold surface pattern on the transparent substrate.
[Patent Document 1]
    U.S. Pat. No. 6,888,676[Patent Document 2]    Japanese Kokai Publication No. 2004-205990